ZyXEL Communications ZYWALL USG 2000 Manual page 330

Unified security gateway

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Table of Contents

Chapter 20 Firewall

• Besides configuring the firewall, you also need to configure virtual servers (NAT

port forwarding) to allow computers on the WAN to access LAN devices. See

Chapter 16 on page 287

• The ZyWALL applies virtual server (Destination NAT) settings before applying

the firewall rules. So for example, if you configure a virtual server that sends

WAN traffic to a LAN IP address, when you configure a corresponding firewall

rule to allow the traffic, you need to set the LAN IP address as the destination.

Section 6.6 on page 138

• The ordering of your rules is very important as rules are applied in sequence.

Figure 212 Firewall

The following table describes the labels in this screen.

Table 102 Firewall

Global Setting

Asymmetrical

for more information.

for an example.

Select this check box to activate the firewall. The ZyWALL performs

access control when the firewall is activated.

If an alternate gateway on the LAN has an IP address in the same subnet

as the ZyWALL's LAN IP address, return traffic may not go through the

ZyWALL. This is called an asymmetrical or "triangle" route. This causes

the ZyWALL to reset the connection, as the connection has not been

acknowledged.

Select this check box to have the ZyWALL permit the use of asymmetrical

route topology on the network (not reset the connection).

Note: Allowing asymmetrical routes may let traffic from the WAN go

directly to the LAN without passing through the ZyWALL. A

better solution is to use virtual interfaces to put the ZyWALL

and the backup gateway on separate subnets.

ZyWALL USG 2000 User's Guide

Troubleshooting